Brachytherapy is a form of cancer treatment in which radiation sources are placed inside a patient's body to irradiate a tumor. In brachytherapy, a surgeon usually implants several radioactive seeds in or around a tumor, thus providing a radiation dose to the tumor. Careful placement of the radioactive seeds allows localized and precise irradiation of the tumor. Because the radiation dose diminishes rapidly outside the radioactive seed, the radiation dose to surrounding healthy tissues is minimized. Many forms of cancer respond to brachytherapy, including several forms of prostate cancer. Brachytherapy generally is less invasive than surgery, usually results in fewer side effects than surgery or external beam radiation, allows for a short recovery time, and reduces the impact on the patient's quality of life.
Radioactive seeds typically are rice grain sized (generally about 0.8 mm by 4.5 mm), roughly cylindrical objects containing very small amounts of radioactive material. In one widely practiced brachytherapy procedure, the radioactive seeds are implanted permanently inside the patient's body. The half-life of the radioactive material is generally short, and the radioactivity in the seeds decays after about three to six months to the point that there is little detectable radiation. Two radioactive isotopes commonly used for permanent implants are iodine-125, often used to treat slower growing tumors, and palladium-103, which is preferred when a tumor is fast growing. Other radioactive materials have been used in implants as well.